The DNS server for Cisco Content Service Switch (CSS) 11000 and 11500, when prompted for a nonexistent AAAA record, responds with response code 3 (NXDOMAIN or βName Errorβ) instead of response code 0 (βNo Errorβ), which allows remote attackers to cause a denial of service (inaccessible domain) by forcing other DNS servers to send and cache a request for a AAAA record to the vulnerable server.